The present invention generally relates to x-ray imaging. In particular, the present invention relates to a system and method for compound x-ray imaging using position sensors.
Digital imaging systems may be used to capture images to assist a doctor in making an accurate diagnosis. Digital radiography and/or fluoroscopy imaging systems typically include a source and a detector. Energy, such as x-rays, produced by the source travel through an object to be imaged and are detected by the detector. An associated control system obtains image data from the detector and prepares a corresponding diagnostic image on a display.
The detector may be a flat panel detector, such as an amorphous silicon flat panel detector, for example. Alternatively, the detector may be an image intensifier or other detecting device, for example. Historically, image intensifier systems produce much distortion. However, current techniques are being used to correct distortion in image intensifier images. For example, passive (e.g., markers in an image) and/or active (e.g., shielding) techniques are being applied to reduce distortion.
Image data obtained from a detector may be used for diagnosis and treatment of diseases and other ailments. For example, Digital Subtraction Angiography (DSA) is an x-ray imaging technique used by interventional radiologists and surgeons to diagnose and treat vascular diseases and conditions. ‘Roadmap’ and ‘Subtract’ are two functions commonly found on mobile and fixed interventional x-ray systems. A fundamental principal of DSA is to subtract one image from another in order to focus attention on image differences. In a typical ‘Roadmap’ sequence, a ‘mask’ image is subtracted from subsequent frames of video. The mask image is acquired while radio-opaque dye contrast is present in a vascular system. Since the dye contrast is not present in subsequent frames, a resultant DSA image shows only the areas where dye contrast was present in the mask. Since other anatomic features were present in the mask and in subsequent frames, the other anatomic features will ‘subtract out’, leaving only a ‘roadmap’ of the vascular system.
One of the challenges with DSA is to maintain registration between the subtraction pair of images. Even small mis-registration due to patient respiration, or c-arm mechanical instability can have a significant negative effect on the resultant image. Although some systems have software features that allow automatic, or manual mask re-registration, re-registration is only practical when solving for small misalignments.
In addition current implementations of DSA require the mask and the subsequent fluoroscopic imaging sequence to be acquired without moving the imaging system with respect to the patient. This lack of movement constrains a region where DSA may be used or requires acquiring new masks each time the imaging system is moved with respect to the patient.
Mobile C-arm systems have become a standard tool for x-ray imaging in intraoperative surgical procedures. Mobile C-arm systems provide x-ray imaging used for successful intervention in a wide variety of surgical interventions. The mobility and relative low cost of mobile C-arm systems make mobile C-arm systems a more flexible imaging solution compared with much larger, more expensive ‘fixed room’ systems.
Although mobile C-arms are becoming more sophisticated in order to meet the needs of new and emerging intervention methods, there are some performance limitations that are constrained by the need to maintain mobility. Compared to a fixed-room system, one such constraint is an inability to link the C-arm and operating table positions and geometries as a single mechanical gantry system.
Image processing techniques, such as ‘image tiling’ and ‘image stitching’, are commonly used in digital photography and are also used by ‘fixed-room’ x-ray systems to expand contiguous image views beyond the limitations normally imposed by image receptor size. These processes are most efficiently achieved when patient position may be determined and/or controlled in relationship to an x-ray image detector.
X-ray fluoroscopy may be used with a contrast dye to perform vascular run-off studies, for example. A contrast dye may be injected into a patient, and a radiologist obtains a series of images from the abdominal aorta into the iliac artery and/or into the left or right leg, for example. As the dye contrast is injected, the C-arm imager is manually moved to follow the day in fluoroscopic imaging. Alternatively, dye may be injected in a first area covered by an x-ray detector to obtain images of the first area. Then, the C-arm is moved to a second area and another dye contrast injection is made to obtain images of the second area. The injection and repositioning process may be repeated until desired images are obtained. Thus, a system and method for improved dye contrast fluoroscopic imaging would be highly desirable. A system and method which minimize an amount of contrast injected in a patient would be highly desirable.
Therefore, there is a need for an improved method and system for compound imaging. There is a need for a system and method for compound x-ray imaging using position sensors. Additionally, there is a need for a system and method for improved image tiling using positional information.